1. Field of the Invention
The present invention relates to a system and method for efficiently and economically dispatching electrical power generated by power stations. More particularly, the present invention continuously monitors operating parameters for each power generating unit in the power stations, calculates the heat rate in real time and monitors exhaust emissions to determine the efficiency of each operating unit, and dispatches the power generated based upon the heat rate and emission efficiency calculations.
2. Description of the Related Art
In modern electrical power generation systems, steam turbines are utilized to generate electrical power. The production of electricity often requires a substantial capital investment to provide the necessary equipment to produce the electricity. In addition, the costs relating to the operation and maintenance of the equipment is also substantial. In an effort to reduce the high operating costs associated with generating electricity, electric utilities attempt to ascertain which steam turbines are operating efficiently and utilize those turbines to generate the power. Inefficient turbines may then be cleaned or serviced while the efficient turbines generate power.
The heat rate of a steam turbine generating unit has long been the key to economic dispatching, and efficient power generation system operation. The heat rate of each turbine provides a dispatch operator with the operational efficiency for each turbine so that the costs associated with placing particular turbines "on-line" can be ascertained and compared to determine which turbine or combination of turbines can generate power at the lowest cost. Currently, the heat rate of a turbine is determined by conducting a series of extensive tests on the turbine, while the turbine is "off-line" and out of service. Such tests are costly and time consuming, and do not provide a "real time" heat rate. The data obtained from the tests is used to develop a series of heat rate curves, which are transferred into an Energy Management Computer System used by the dispatch operators to dispatch the power generated. When making dispatch decisions, such as determining which turbines should be placed "on-line" and for what period of time, or determining when to buy power from other utilities instead of generating the power, or determining to generate power which can be sold to other utilities for a profit, it becomes increasingly important to have accurate heat rate data and curves.
Since the heat rate data is currently obtained by taking each turbine out of service for a period of time, the costs associated with performing the test and obtaining the heat rate data is substantial. As a result, heat rate measurements are typically performed on each turbine once or twice a year.
Because the actual heat rate data is obtained relatively infrequently, various problems arise in the dispatching of the electrical power. One problem associated with current heat rate measuring techniques is that minor deviations in the heat rate occur from, for example, normal wear and tear of the turbine, performance degradation of condensers, air and water temperatures supplied to the turbine, and the quality of the fuel supply. More significant deviations in the heat rate occur when the equipment utilized to generate the power, such as water pumps and forced air blowers, are either out of service or running at a reduced efficiency rates. When the heat rate deviations occur between the time of the actual heat rate determinations, e.g., typically, once or twice a year, the dispatch operator does not have accurate heat rate data to economically dispatch the power generation. As a result, instances occur where dispatch operators place turbines "on-line" which are operating below maximum efficiency. Thus, the price charged to customers does not accurately reflect the cost to the utility to generate the power and the profit margin may be reduced or the utility may be selling the electricity to customers or other utilities at a loss.
Another problem associated with dispatching electrical power from inaccurate heat rate data occurs when dispatching the power between utilities connected to power grids. When dispatching power generation, the costs of power generation, the purchase of fuel, and the sale of power between utilities is carefully calculated to provide maximum cost advantages for the utility. The costs associated with the operation of each turbine, whether it is in operation (i.e., "on-line") or on stand-by (i.e., "off-line"), are compared with the costs of purchasing power available from other utilities and the possible sale of power to other utilities. For example, in certain instances the dispatch operator may place a turbine "on-line" for the primary reason of selling the power generated at a profit to another utility, or the dispatch operator may place a turbine "off-line" if power can be purchased from another utility for less than the cost of generating the power locally. However, if the heat rate data used to dispatch the electric power is inaccurate, any cost savings believed to be achieved may also be inaccurate.
To efficiently and economically produce the electricity, electric utilities have utilized data acquisition and control systems to dispatch electric power. Existing data acquisition and control systems have evolved around the concept of a centralized data acquisition processor and a common database which provides data to dispatch operators for dispatching of the power generation. Many of the current designs utilize sensors extending into predetermined data acquisition points within the power generation system. These sensors acquire data relating to the status and efficiency of the turbines. However, these systems do not solve the problem of out-of-date heat rate data.
Another drawback to such centralized data acquisition and control systems is that the failure of one element within the system may render the entire data system inoperable making it impracticable for the dispatch operator to economically dispatch the power. Furthermore, as the common database of such a centralized system increases in size, the processing load on the central processor reduces the ability of the data acquisition and control systems to operate in real time.
An additional factor which should be incorporated into the economic dispatching of electrical power, is the quality of the exhaust emissions generated by operating each turbine. To illustrate, boilers are utilized to generate steam for the turbines. Each boiler burns fuel (either oil, gas, coal, wood, or the like or a mixture thereof) and emits exhaust gases and particles into the atmosphere via exhaust stacks. Before permitting the exhaust gases and particles to travel up the exhaust stack, many generating units filter or scrub the exhaust to clean out undesirable contaminants in order to satisfy governmental guidelines on the amounts of contaminants that may be released into the atmosphere in a given period of time. Because of these guidelines, the question of which turbine to utilize, at what capacity and for how long, not only depends on the economics of power generation versus power transactions, but also on the emission quality associated with each possible operational configuration of the turbines.
In order to properly determine which operational configuration, i.e., the number of turbines and which particular turbines, should be utilized, computer systems are utilized to continuously evaluate the emission quality exiting the exhaust stacks for each turbine. However, such computer systems are passive systems which do not respond to the data received from the exhaust emissions, i.e., these systems simply provide the dispatch operator with reports reflecting the quality of each turbine.
Therefore, a need exists for a data acquisition system which ascertains heat rate data in real-time to continuously provide dispatch operators with accurate heat rate data for optimum dispatching of the electrical power. A need exists for a system which incorporates emission quality data into the dispatching of the electrical power. Further, a need exists for a decentralized power generation system constructed in modules which are interconnected by a data network to prevent overloading of a single processor as well as to reduce the effects of a single malfunction on the entire system.